Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/14/20
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
1055 PM CDT Fri Mar 13 2020
.UPDATE...
Issued at 1050 PM CDT Fri Mar 13 2020
Have made some minor adjustments to POP and WX grids based on
radar, satellite and model trends. Thoughts below:
1) Have added some drzl/frz drzl. Areas without significant radar
returns are probably seeing this due to lack of saturation in DGZ.
These areas are transient and given marginal sfc temps near
freezing, doubt there will be much impacts. Perhaps some lt glaze
on elevated surfaces.
2) We`ve been in a lull late this eve, but models show uptick in
QPF in the 06Z- 12Z time frame. Thus, have not made any
significant changes to snow amounts. There`s still factors of
warm ground and wet snow/low ratios fighting against higher
amounts. Still think most areas in advisory will see 3-5", with
some isolated areas near 6" still possible. However, so far,
impacts to roads has been fairly minimal.
3) Didn`t make any headline changes on this shift, but may very
well need to move up the end time as most, if not all, appreciable
QPF should be done by ~15Z. Caveat to this could be lingering
potential for fzdz. However, even by 18Z will likely see temps
rise 1-2 deg, which combined with March sun angle, would be
enough to eliminate icing threat. Will let midshift coordinate
with neighbors on this potential update.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 342 PM CDT Fri Mar 13 2020
Aloft: As has been the case since mid-Nov...mainly zonal flow
remains over the CONUS. Aircraft wind obs and RAP dynamic
tropopause analyses indicated anticyclonic WSW flow over NEB/KS. A
shrtwv trof extended from the UT-CO border down into AZ. This
trof will lift NE and cross the CWA late tonight into tomorrow AM.
Heights will rapidly rise in its wake...with a broad ridge
forming over the Plns in response to the next low diving S along
the W coast.
Surface: 1050 mb high pres over Wrn Canada extended SE into the
Cntrl USA. The cool front that moved thru here Thu AM was over
Cntrl TX and the Gulf Coast states. Weak low pres will form along
that front tonight into tomorrow...while high pres conts to
dominate acrs Srn Canada. That will keep E winds over the CWA thru
tomorrow.
Rest of this afternoon: Radar mosaic shows predominantly -SN
overtaking the CWA. The leading edge is not reaching the ground
due to low-lvl dry air. Where temps have climbed into the low
40s...the leading edge of pcpn reaching the ground was falling as
-RA. Expect RA/SN to cont advancing NE.
NDOT traffic cams indicated snow accumulating on grassy areas
along Hwy 136 W of Riverton. Snow is probably accumulating over
Gosper/Phelps counties as well. With temps above frzg and
concrete/pavement still absorbing insolation...the snow was
melting on contact. So roads were just wet attm.
Tonight: Snow will overtake the entire CWA. Once the sun goes
down and roads and temps cool...snow will begin accumulating on
roads. Temps will fall to near 32F and hold steady. The latest
blend of mdl QPFs came in a touch higher than prvs fcsts. Snow
ratios were capped at 10:1 given near-frzg temp profile. That
still resulted in some 6" amts over parts of
Dawson/Gosper/Phelps/Furnas counties.
Winter Wx Advy conts as posted at 4 AM...but the possibility of 6"
amts necessitated upgrading Dawson/Gosper/Phelps/Furnas to a
wrng.
Given that this is a weak system...and no strengthening
expected...and initial melting and compaction due to warm
ground...most locations should remain at or below 5". Expect a
gradient of 1-5" from SE-NW acrs the CWA with isolated 6" psbl in
the warning area.
Sat: Snow will taper off and end during the morning from SW-NE.
There`s a chance a little snow could linger into early afternoon N
and E of I-80...but the accumulating snow will be over. Highs in
the 30s.
Wind will not be a big issue with this system as there is no sfc
low anywhere nearby. E 10-20 mph with some gusts around 25 mph at
times.
The wet character of the snow will minimize blowing and drifting.
After the snow ends...remaining cldy. There is a chance that some
patchy drzl could occur.
.LONG TERM...(Saturday night through Friday)
Issued at 342 PM CDT Fri Mar 13 2020
Aloft: Low-amplitude anticyclonic W-WSW flow will cont over
NEB/KS thru Tue...as a strong low sinks down the W coast...a low
remains over Hudson Bay...and a subtropical high remains parked
over the Caribbean. The W coast low is fcst to creep slowly inland
Wed and this will back winds to SW over the CWA. Some
acceleration is psbl Thu as another low dives into the backside of
the longwave trof. The last 2-3 runs of the EC/GFS-FV3/CMC are
now consistent on lee cyclogenesis Thu night with a new low
forming and briefly intensifying over NEB. It is then fcst to
weaken on its way into the upr Midwest Fri.
Surface: The strong high over Srn Canada will head E Sun. A very
wk cool front will form over the Nrn Plns Sun night and it will
cross the CWA Mon eve. Behind this front...another big Canadian
high will gradually slide ESE into New Eng by Wed. In the
meantime...the cool front will become stationary over the Srn
Plns. Lee cyclogenesis will begin over CO Wed. This will force the
front to lift back N as a warm front. The CO low will intensify
Thu. This is still a week out...so there are timing/location diffs
between the mdls...but that low is fcst to eject out acrs NEB/KS
Thu night into Fri. The warm front will probably lift as far N as
the state line. Meanwhile...a Canadian cold front will drop S Thu
night and merge with this system...increasing the temp grad.
Temps will average at or below normal thru next Fri. The
chilliest day will be Sun. Don`t expect much increase in temps
before Thu as this entire fcst is looking very cldy. We could see
a temporary pop in temps Thu as the warm front gets close...but
the cool front will quickly follow Fri.
Precip: As with yesterday...NBM has a lot of pops/precip chances
that I really don`t think are warranted for large portions of time
between Sat night thru Mon night. Am not saying it will be
completely dry...but whatever falls will be very light and minor.
Changed the character of the precip to drzl as clds will be very
shallow and all liquid/no ice. The next legit rain chances will
arrive Tue night into Wed and then Thu-Fri. Rumbles of thunder
still possible...espcly Thu night. This Thu-Fri system could be a
soaker for S-cntrl NEB...espcly W and N of the Tri-Cities. Hvy wet
snow will be psbl NW fringe of the CWA.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday)
Issued at 653 PM CDT Fri Mar 13 2020
Significant wx: Prolonged period of IFR conditions.
Tonight: High confidence for IFR CIGs and VSBYs. Minimum CIGs and
VSBYs could drop to LIFR at times during heaviest bands. E winds
will gradually incr this eve, with gusts 20-25kt overnight. Expect
2-5 inches of snow accumulations during this time.
Saturday: High confidence IFR CIGs through much, if not all of
daytime hrs Sat. IFR VSBYs will most likely be ongoing at start
of the period in continued -SN. Additional inch or so of
accumulation expected 12-18Z. Eventually, expect VSBYs to improve
to MVFR levels by mid to late morning as snow decr, but lingering
boundary layer moisture and upslope component to winds may allow
light fog to continue thru daytime. Expect continued IFR CIGs and
return to IFR VSBYs Sat night.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Winter Weather Advisory until 4 PM CDT Saturday for NEZ039>041-
046>049-061>064-074>077-083>086.
Winter Storm Warning until 4 PM CDT Saturday for NEZ060-072-073-
082.
KS...Winter Weather Advisory until 4 PM CDT Saturday for KSZ005-006.
&&
$$
UPDATE...Thies
SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Thies
Area Forecast Discussion
National Weather Service Great Falls MT
859 PM MDT Fri Mar 13 2020
.SYNOPSIS...
A major winter storm will continue to impact the Northern Rockies
tonight and through the day on Saturday. Snow, blowing snow, and
cold temperatures will accompany this storm, with the worst
conditions expected across North Central and Central Montana. Near
blizzard like conditons are even possible between the Rocky
Mountain Front and Interstate 15 corridor tonight.
&&
.UPDATE...
The evening update has been published. Winter storm continues with
the most impacts being observed just northwest of a Helena to
Great Falls line. Periods of heavy snow and strong winds will
continue in these areas for much of the night. Further east
precipitation has been slower to materialize but it should
increase during the overnight hours. No changes were made to the
current winter headlines and only minor adjustments were made to
the current forecast.
&&
.AVIATION...
Updated 600 PM MDT Fri Mar 13 2020 (14/00Z TAF Period)
Snowy conditions with gusty winds are expected for the Central/North-
central terminals through Saturday afternoon and likely the entire
period for KLWT, and KHVR. This will result in widespread MVFR-LIFR.
Winds will gradually become more northerly from west to east tonight
into Saturday morning. The southwest terminals will likely observe
falling ceilings tonight, with chances for snow showers increasing
after 4Z. MVFR conditions can be expected with some IFR, mostly for
KWYS. Mountian obscurations and aircraft icing is expected.
&&
.PREV DISCUSSION...
/ISSUED 609 PM MDT Fri Mar 13 2020/
Rest of this afternoon through Saturday night...the biggest concern
and focus with the afternoon forecast has been on the winter storm
now impacting the region, in addition to the potential for record to
near record low temperatures Saturday night/Sunday morning across
North Central and Central Montana.
Snow has developed along the Rocky Mountain Front as expected early
this morning, and has been slowly backing/advancing eastward over
the plains of North Central and Central this afternoon. Easterly low
to mid-level winds have and will continue (for portions of the
evening) lead to precipitation shadowing immediately to the west of
the Island Ranges (i.e. Sweet Grass Hills, Highwood, Bears Paw,
Moccasin, Judith, Snowy, and Little Rocky), which will ultimately
lead to lower snowfall totals of 4-7" here (portions of Eastern
Cascade, Western Fergus, Eastern Chouteau, and Eastern Toole
Counties). Elsewhere, snowfall totals by the end of the storm Sunday
morning will generally range from 10-20" along west of the I-15
corridor and north of the Montana Highway 200 corridor, to 7-14"
east of the I-15 corridor and across the remainder of North Central
and Central Montana. Across Southwest Montana, lower elevation
snowfall of 2-6" is generally expected, with 6-12" at pass level and
in the mountains along the Idaho/Wyoming border. All of the Winter
Storm Warnings remain in place across the region, and Winter Weather
Advisories are now in place for all of Southwest Montana. Travel
will become very difficult and hazardous this evening and during the
overnight hours across North Central and Central Montana, especially
along and west of the I-15 corridor. Here a push of 6hr pressure
rises of 3-6mb along the Rocky Mountain Front combined with H850
winds of 25-35kts are expected to lead to a prolonged period of
strong and gusty northerly winds. While blizzard conditions remain a
possibility, especially between 00z-09z Saturday, confidence remains
to low to issue blizzard highlights. None-the-less, intense snowfall
rates of 1-2" per hour during this timeframe and at these locations
combined with the winds will likely lead to near-blizzard like
conditions. Finally, a very cold night is expected Saturday
night/Sunday morning as a strong surface high settles over the area,
with the potential for record or near-record temperatures. -Moldan
Sunday through Next Friday...A shortwave moves northeast through
southwest Montana Montana into eastern portions of plains during
the day on Sunday. This will keep snow going over these areas with
the most impacts being confined to the southwest. The Winter
Weather Advisory issued for the southwest handles the anticipated
impacts well.
Upper level troughing remains over the region through next week for
continued cooler than average conditions, especially considering the
snow pack that should be in place after the storm this weekend. A
mid-upper level low center within the broader upper trough is
expected to slowly drop southward along the CA coast early next week
before swinging through the SW US and eventually ejecting out into
the central US Plains region late next week. This trajectory would
keep the threat for significant precipitation mostly to the south of
the forecast area, but some weak energy does looks to move through
the region late Wednesday through Friday and the low lifting NE into
the central US is close enough to bear watching as any shift
northward in its track would bring greater precipitation chances to
the forecast area. Temperatures will moderate through the first half
of next week but likely max out in the 20s and 30s for most of north-
central MT while warming into the 40s in SW MT valleys by Tuesday
and Wednesday. As low pressure passes south of the region Thursday
and Friday some colder air will likely be drawn south from Canada
into Montana.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 1 6 -10 13 / 100 100 100 40
CTB -8 0 -13 11 / 100 100 40 20
HLN 3 11 -2 23 / 100 100 80 50
BZN 14 27 5 30 / 30 40 80 80
WYS 16 33 19 39 / 70 100 100 90
DLN 20 32 13 34 / 20 30 70 70
HVR 12 20 4 20 / 100 100 100 40
LWT 16 22 0 18 / 90 90 100 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 4 PM MDT Saturday Broadwater...
Jefferson.
Winter Storm Warning until 4 PM MDT Saturday Central and
Southern Lewis and Clark.
Winter Storm Warning until 6 AM MDT Sunday Blaine...Cascade...
Chouteau...Fergus...Hill...Judith Basin...Liberty.
Winter Weather Advisory from 6 AM Saturday to 6 PM MDT Sunday
Beaverhead...Gallatin...Madison.
Winter Storm Warning until 6 AM MDT Sunday Meagher.
Winter Storm Warning until 4 PM MDT Saturday Eastern Glacier...
Eastern Pondera...Eastern Teton...Northern Rocky Mountain
Front...Southern Rocky Mountain Front...Toole.
&&
$$
http://www.weather.gov/greatfalls